joshluther

iTrader: (24)

Will it work at all? There are quite a few tables in HPT for the fuel sender. Am I just wasting my time?

rsz288

The stock PCM/ECM expects a 240 ohm sender which varies from 40ohms empty to 240 ohms full (or something like that), so a 90 phm sender would probably read below a quarter when full and set a DTC when it went below 40ohms. Unfortunately.......

joshluther

iTrader: (24)

I guess I might experiment with some settings before I swap out the sender.

techrunner

iTrader: (4)

i am very interested in this. that looks like it might solve the issues for the old 0-90 sender and if thats all it takes it would be a much easier and better way then hacking all that stuff up in the tank. is there anything in there that would let you change the output to the gauge only? if you could leave the sender alone, and theres a gauge output that you could program to 0-90 ohm use that'd save me a ton of screwing around with the tank sender. keep us posted. thanks a lot

91ZLS6

iTrader: (2)

Am i missing something? Why do you want your PCM to know your fuel level? It uses fuel level to do EVAP calculations and run a serial data fuel level.

If you've got a fuel level gauge already, and your not running a computer controlled EVAP system, what do you want it to know the fuel level for?

But yes, you can modify the fuel level input and volume of the tank.

techrunner

iTrader: (4)

i am wondering if there is a workaround in the tuning to get it to output a 0-90 fuel level signal to control a gauge. i have a 01 camaro tank going into a 91 formula, and i am keeping all the original gauges in place. if theres an output form the pcm that i can convert to 0-90 somehow, that'd be better than having to jerry-rig my 91 sender into my 01 tank

91ZLS6

iTrader: (2)

No their is not.

The computer has a fuel level input, but no output. Im guessing you havent really looked into the gauge control system on the 99+ LS1's.

The oil pressure gauge is direct from the sensor, the volt meter is from the alternator, and the rest are serial data driven. It takes an input in, and puts the data out as Class 2 serial data.

I put a '00 tank in my '89, and the only way to make it run your gauge is to take out the old fuel sender, and get creative with putting a 0-90 to get your stock thirdgen gauge to work.

The fuel level input is for MPG & EVAP calculations. Unless you somehow make your 91's gauges control from solid state logic, it aint gonna be working. trust me, ive been down this road trying to make it work, its not going to happen.

techrunner

iTrader: (4)

thats what i thought, and that was my plan until i saw this post. it just got me wondering about any kind of output that could be added into the tune, if the program gives the ability to have any kind of analog output programmed into the code to translate. oh well.

joshluther

iTrader: (24)

I have a car pc with a touch screen as my dash. I use HPtuners for all my gauges except my fuel level. Just trying something different I guess.

There is a gauge output vs. level table for PWM here is another screen shot.

rsz288

The PCM/ECM's typically sense for a voltage of 2.5V when full (1/2 of the 5V supply rail) and around 0.15V when empty so any sender setup needs to achieve this. And as 91ZLS6 points out, there is no fuel guage output other than on the serial bus/CAN.

A PC based dash that can access the % fuel level parameter would no doubt give a meaningful level indication.

The other hitch with this is if the existing OS in the PCM is set for dual senders. Lots of luck. Been there.

The other thing the fuel tank level sensing does is activate flex fuel PCM's with virtual fuel sensing to start calculating the % ethanol in the fuel when the tank is re-filled.

CalEditor

iTrader: (1)

I am under the impression that when the PCM detects a given amount of knock the PCM switches to the low octane table. Do we all agree on this?

Now really think about this!
What input is needed to switch back to the High Octane Table?
A key cycle?

I am under the impression it is only after you fill the tank, so you need the fuel level sensor input.

So who is stuck on a low octane table?

If you think you aren't prove it. Zero out the low octane and add 10° to the High octane table and then monitor the spark timing

That would be funny

CalEditor

iTrader: (1)

I am working out the bugs in one currently

rsz288

the ECM doesnt jump straight to the low octane table, any knock and severity of knock sets a factor between 0 & 1 that causes timing to operate at the hi table (0) and the low table (1) and anywhere in between.

Absence of knock sees this factor learn back towards zero and the hi table. Learn rate varies from within a few minutes, to considerably longer. Must take a look some time and see what tank level does in terms of reset rate.

CalEditor

iTrader: (1)

So you get your self on the low octane table. How and Why would the PCM ever switch back.

rsz288

Is that a trick question?

CalEditor

iTrader: (1)

The PCM has to see the tank full to run the octane level or Volatility test depending on the OSID

91ZLS6

iTrader: (2)

Im going to do some more research into this, i think your wrong about this.

I know forsure my computer is switching between high and low tables as i have high and low octane fuels in the car, and the computer has no idea what my fuel level is.

Therefore if it needed a fuel level input i wouldnt be seeing a switch between tables.

rsz288

Ditto. ECM being currently run here does not even have a tank input and it sets the Octane Scaler/Knock Learn Factor depending on knock and interpolates between the hi and lo table and heads back to the hi table when there is no knock. Smart little gizmo it is.

CalEditor

iTrader: (1)

What software are you using, what OSID # are you talking about and what PCM # are you talking about?

I have GM documents that state different. I have proven this different already.

I will get some pictures together

rsz288

2008 E38 ECM. What vintage are the GM docs that state that a tank fill is needed?